package Sort;

public class Sort {

    public static void mergeSortFunc(int[] array,int left,int right) {
        if(left == right) {
            return;
        }
        int mid = (left + right) / 2;
        //分解
        mergeSortFunc(array,left,mid);
        mergeSortFunc(array,mid+1,right);

        //合并操作
        merge(array,left,right,mid);
    }

    private static void merge(int[] array, int left, int right, int mid) {
        int s1 = left;
        int e1 = mid;
        int s2 = mid+1;
        int e2 = right;
        int[] tmpArr = new int[right-left+1];
        int k = 0;
        //此时2个数组 都至少有一个数据
        while(s1 <= e1 && s2 <= e2) {
            if(array[s1] <= array[s2]) {
                tmpArr[k++] = array[s1++];
            }else{
                tmpArr[k++] = array[s2++];
            }
        }
        while (s1 <= e1) {
            tmpArr[k++] = array[s1++];
        }
        while (s2 <= e2) {
            tmpArr[k++] = array[s2++];
        }
        //保证tmpArr当中的元素是有序的
        for (int i = 0; i < tmpArr.length; i++) {
            array[i+left] = tmpArr[i];
        }
    }

    public static void mergeSort(int[] array) {
        int gap = 1;
        while (gap < array.length) {
            for (int i = 0; i < array.length; i += 2*gap) {
                int left = i;
                int mid = left+gap-1;
                int right = mid+gap;
                if(mid >= array.length) {
                    mid = array.length-1;
                }
                if(right >= array.length) {
                    right = array.length-1;
                }
                merge(array,left,right,mid);
            }
            gap *= 2;
        }
    }





}
